What Climate Change on Exoplanets Tells Us About Future of Life on Earth… Doooohhhh… Not so Good…

I chat about a recent peer-reviewed scientific paper studying exoplanets that orbit other stars in other solar systems.

“The Earth is a wonderful blue and green dot covered with oceans and life, while Venus is a yellowish sterile sphere that is not only inhospitable but also sterile. However, the difference between the is only a few tens of degrees in temperature. A team of astronomers… has achieved a world’s first by managing to simulate the entirety of the runaway greenhouse process which can transform the climate of a planet from idyllic and perfect for life, to a place more than harsh and hostile. The scientists have also demonstrated that from initial stages of the process, the atmospheric structure and cloud coverage undergo significant changes, leading to an almost-unstoppable and very complicated to reverse runaway greenhouse effect. On Earth, a global average temperature rise of just a few tens of degrees, subsequent to a slight rise of the Sun’s luminosity, would be sufficient to initiate this phenomenon and to make our planet inhabitable. These results are published in Astronomy & Astrophysics.”

“The idea of a runaway of the greenhouse effect is not new. In this scenario, a planet can evolve from a temperate state like on Earth to a true hell, with surface temperatures above 1000°C. The cause? Water vapor, a natural greenhouse gas. Water vapor prevents the solar irradiation absorbed by Earth to be reemitted towards the void of space, as thermal radiation. It traps heat a bit like a rescue blanket. A dash of greenhouse effect is useful – without it, Earth would have an average temperature below the freezing point of water, looking like a ball covered with ice and hostile to life.

On the opposite, too much greenhouse effect increases the evaporation of oceans, and thus the amount of water vapor in the atmosphere. “There is a critical threshold for this amount of water vapor, beyond which the planet cannot cool down anymore. From there, everything gets carried away until the oceans end up getting fully evaporated and the temperature reaches several hundred degrees,”

“One of the key points of the study describes the appearance of a very peculiar cloud pattern, increasing the runaway effect, and making the process irreversible. “From the start of the transition, we can observe some very dense clouds developing in the high atmosphere. Actually, the latter does not display anymore the temperature inversion characteristic of the Earth atmosphere and separating its two main layers: the troposphere and the stratosphere. The structure of the atmosphere is deeply altered,”

Article:
“Exoplanets’ climate – it takes nothing to switch from habitable to hell.”
https://www.aanda.org/component/content/article/208-press-releases/2023-press-releases/2930-exoplanets-climate-it-takes-nothing-to-switch-from-habitable-to-hell

“The Earth is thus not so far from this apocalyptical scenario. “Assuming this runaway process would be started on Earth, an evaporation of only 10 meters of the oceans’ surface would lead to a 1 bar increase of the atmospheric pressure at ground level. In just a few hundred years, we would reach a ground temperature of over 500°C. Later, we would even reach 273 bars of surface pressure and over 1 500°C, when all of the oceans would end up totally evaporated,”

A few tens of degrees C to trigger this runaway greenhouse effect may seem like a lot, but it’s not. Remember than James Hansen’s climate sensitivity value is a nominal 4.8C (actually between 3.6C and 6.0C) so it’s not too far off.

Here is the title and link to the open-source peer reviewed paper:
“First exploration of the runaway greenhouse transition with a 3D General Circulation Model”
https://www.aanda.org/articles/aa/full_html/2023/12/aa46936-23/aa46936-23.html

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by paulhenrybeckwith